x/1*3+x/3*5+x/5*7+x/7*9+.x/2011*2013=2012
x/2(1-1/3+1/3-1/5+1/5-1/7+.+1/2011-1/2013)=2012
x/2(1-1/2013)=2012
1006x/2013=2012
x=4026